1. Field of the Disclosure
The present disclosure relates to touch panels, and in particular relates to the main spacer and the sensor spacer thereof and methods for manufacturing the same.
2. Description of the Related Art
Many input devices such as key board/mouse/trackball or recently key board/mouse/touch panel are integrated into single, commercially available, electronic products, thereby largely improving the input efficiency and convenience thereof. The developmental trend of electronic products towards to be light, thin, short, small, and multifunctional. It is difficult to integrate many input devices into one electronic product. However, touch panels may simultaneously include several operating functions applied by input devices such as oard, mouse, or others (e.g. handwriting recognition). Compared to the conventional input devices, touch panels offer not only input functions but also output functions. Accordingly, touch panels are currently considered a mature and stable technology, to be employed as an input device. Additionally, because of its advantageous characteristics, touch panels are the top choice selected by the industry designer to develop related displays for human-machine interface. For example, touch panels are widely applied as input devices in personal digital assistances (PDA), e-books, mobile phones, laptop computers, and global positioning systems (GPS).
Referring to the driving modes of touch panels, they are categorized into resistive type, capacitive type, sonic type, optical waveguide type, load weight change type, and the likes. Resistive touch panels are currently one of the most applied touch panels in commercial products, and their designs are further separated into four lines, five lines, six lines, and the likes; often distinguished by companies.
FIG. 1A shows a cross section of a conventional touch panel. The top substrate of the touch panel 100 is a color filter substrate 10A, and the bottom substrate thereof is an array substrate 10B. The color filter substrate 10A includes a substrate 20, a color filter 22, a black matrix 24, an overcoat layer 26, a main spacer 11, a sensor spacer 15, and a conductive layer 19. The array substrate 10B includes a substrate 20, a first metal layer 101, a gate insulation layer 103, a semiconductor layer 105 made of material such as amorphous silicon or n-type doped amorphous silicon, a second metal layer 107, a protection layer 109, a contact pad 17A, and a pixel electrode 17B made of material such as indium tin oxide. The array substrate 10B further includes a stacked structure 13 sequentially constituted from bottom to top as: the first metal layer 101, the gate insulation layer 203, the semiconductor layer 105, the second metal layer 107, and the protection layer 109. The cell gap between the top and bottom substrates 10A and 10B is defined by the total height of the main spacer 11 and the stack structure 13. The contact pad 17A of the array substrate 10B corresponds to the sensor spacer 15 of the color filter substrate 10A. After the formation of the main spacer 11 and the sensor spacer 15 from a single lithography process, the conductive layer 19 is formed on the spacers. In other words, the conductive layer 19 is conformally formed on the spacer (e.g. the main spacer 11 and the sensor spacer 15) surface and the overcoat layer surface. Thus, the spacers do not contact the entire surface of the overcoat layer. Accordingly, when a user presses the touch panel 100, the conductive layer 19 on the sensor spacer 15 will contact the contact pad 17A to input a signal. Note that the surface of the main spacer 11 is covered by the conductive layer 19. Additionally, when a user presses the touch panel, the main spacer 11 in a non-pressed region may easily deviate from a tolerance range A of the stack structure 13 by the physical force to contact a nearby pixel electrode 17B. In this case, unexpected bright points would be produced due to shorting. Increasing the area of the stack structure 13 may solve the described problem, but the aspect ratio of the touch panel would concurrently decrease.
Thus, to solve the described problem, adjustments are further made. The main spacer 11 and the sensor spacer 15 in FIG. 1B are formed in different processes, respectively. In FIG. 1B, the sensor spacer 15 and the conductive layer 19 are formed, and the main spacer 11 is then formed, such that the surface of the main spacer 11 is free of any conductive layer. When a user presses the touch panel 101, even if the main spacer 11 in the non-pressed region deviates from the tolerance range A of the stack structure 13 by the physical force, the contact of the main spacer 11 (its surface is free of the conductive layer) with the nearby pixel electrode 17B will not produce unexpected bright points due to shorting. Therefore, it mitigates the bright points or low aspect ratio problems in FIG. 1A. However, the two processes for forming two spacers produce larger film thickness variation, which increase the cell gap variation between the top and bottom substrates. The main and sensor spacers 11 and 15 formed by the single lithography process in FIG. 1A have a height error value of ±0.15 μm. The main and sensor spacers 11 and 15 formed by the two lithography processes in FIG. 1B have a height error value of ±0.3 μm. Accordingly, sensor gap variations between the conductive layer 19 on the sensor spacer 15 and the contact pad 17 is largely increased by greater height error values, such that different display regions of the touch panel 101 have different touch sensitivities.
Accordingly, a solution is called for the conductive layer on the main spacer problem come from the single lithography of forming the mains spacer and the sensor spacer.